Trying to convert Go Pro GYRO Data to rotation in Three.js - javascript

I'm trying to convert Go Pro gyro data to Three.js coordinates so that I can project the footage onto the inside of a sphere, rotate the sphere and have 3D stabilisation.
The camera is orientated as such, and the order of the coordinates is Z,X,Y
I'm attempting to apply this vector to rotate the sphere, something like this
this._nextVec3.set(this._next[0],this._next[1],this._next[2])
this.el.object3D.rotation.setFromVector3(this._nextVec3)
But I can't get the rotation to match the rotation of the camera, and I assume it's something to do with the left/right hand configuration?
Can anyone help?

First of all, make sure you specify the correct rotation.order attribute. Since you said it's ZXY, then it should be a simple
this.el.object3D.rotation.order = "ZXY";
Secondly, check out the Three.js axes, taken from the editor:
As you can see, the WebGL axes are different than the GoPro. I think you'll have to flip the X-axis, and swap the Z and Y. So maybe something like:
let xRot = this._next[0];
let yRot = this._next[1];
let zRot = this._next[2];
this.el.object3D.rotation.set(-xRot, zRot, yRot);

Related

three.js: finding nearest point of a Mesh to mouse cursor

Imagine this three.js scene, set up with an OrthographicCamera and OrbitControls:
When the user drags the yellow disc (meant to represent the Sun), the disc needs to move along its yellow circle in response to this action. Here's the scene from another angle, so you can see the full yellow circle:
So, my event handler must determine which point on this circle is closest to the current cursor position. This yellow circle is a THREE.Mesh, by the way.
I'm using THREE.Raycaster to determine some mouseover events, using its intersectObjects() function, but it's not clear to me how to find the nearest point of a single object with this Raycaster. I'm guessing there is some simple math I can do after translating the mouse's position to world co-ordinates. Can someone help me with this? Is Three.js's Raycaster useful here? If not, how do I determine the nearest point of this mesh?
The full source code is here, if it's helpful: https://github.com/ccnmtl/astro-interactives/blob/master/sun-motion-simulator/src/HorizonView.jsx Search for this.sunDeclination, which corresponds to the yellow circle's Mesh object.
For a working demo, go here: https://ccnmtl.github.io/astro-interactives/sun-motion-simulator/
For reference, the sun should behave like this: https://cse.unl.edu/~astrodev/flashdev2/sunMotions/sunMotions068.html (requires Flash)
The simplest version:
get a point on disk
make a projection in the plane of the circle
knowing the radius of the circle, calculate the multiplier for multiplying the vector by the scalar
var point = res.point.clone();
point.z = 0; // Project on circle plane
var scale = circleRadius / point.length();
point.multiplyScalar(circleRadius / point.length())
[ https://jsfiddle.net/c4m3o7ht/ ]
The raycaster returns all objects hit by the ray.. all of the hit points in worldspace.. (which you can convert to/from model space via object3d.worldToLocal and localToWorld)
It returns the hit distances.. which you can sort by whatever heuristic you need...
What I usually do is cast on mouseDown.. record the object and point.. then on mouseMove get the same objects hit point, and apply my edit operation using the difference between those 2 points.
Is this what you're talking about?

How do I 'wrap' a plane over a sphere with three.js?

I am relatively new to three.js and am trying to position and manipulate a plane object to have the effect of laying over the surface of a sphere object (or any for that matter), so that the plane takes the form of the object surface. The intention is to be able to move the plane on the surface later on.
I position the plane in front of the sphere and index through the plane's vertices casting a ray towards the sphere to detect the intersection with the sphere. I then try to change the z position of said vertices, but it does not achieve the desired result. Can anyone give me some guidance on how to get this working, or indeed suggest another method?
This is how I attempt to change the vertices (with an offset of 1 to be visible 'on' the sphere surface);
planeMesh.geometry.vertices[vertexIndex].z = collisionResults[0].distance - 1;
Making sure to set the following before rendering;
planeMesh.geometry.verticesNeedUpdate = true;
planeMesh.geometry.normalsNeedUpdate = true;
I have a fiddle that shows where I am, here I cast my rays in z and I do not get intersections (collisions) with the sphere, and cannot change the plane in the manner I wish.
http://jsfiddle.net/stokewoggle/vuezL/
You can rotate the camera around the scene with the left and right arrows (in chrome anyway) to see the shape of the plane. I have made the sphere see through as I find it useful to see the plane better.
EDIT: Updated fiddle and corrected description mistake.
Sorry for the delay, but it took me a couple of days to figure this one out. The reason why the collisions were not working was because (like we had suspected) the planeMesh vertices are in local space, which is essentially the same as starting in the center of the sphere and not what you're expecting. At first, I thought a quick-fix would be to apply the worldMatrix like stemkoski did on his github three.js collision example I linked to, but that didn't end up working either because the plane itself is defined in x and y coordinates, up and down, left and right - but no z information (depth) is made locally when you create a flat 2D planeMesh.
What ended up working is manually setting the z component of each vertex of the plane. You had originaly wanted the plane to be at z = 201, so I just moved that code inside the loop that goes through each vertex and I manually set each vertex to z = 201; Now, all the ray start-positions were correct (globally) and having a ray direction of (0,0,-1) resulted in correct collisions.
var localVertex = planeMesh.geometry.vertices[vertexIndex].clone();
localVertex.z = 201;
One more thing was in order to make the plane-wrap absolutely perfect in shape, instead of using (0,0,-1) as each ray direction, I manually calculated each ray direction by subtracting each vertex from the sphere's center position location and normalizing the resulting vector. Now, the collisionResult intersection point will be even better.
var directionVector = new THREE.Vector3();
directionVector.subVectors(sphereMesh.position, localVertex);
directionVector.normalize();
var ray = new THREE.Raycaster(localVertex, directionVector);
Here is a working example:
http://jsfiddle.net/FLyaY/1/
As you can see, the planeMesh fits snugly on the sphere, kind of like a patch or a band-aid. :)
Hope this helps. Thanks for posting the question on three.js's github page - I wouldn't have seen it here. At first I thought it was a bug in THREE.Raycaster but in the end it was just user (mine) error. I learned a lot about collision code from working on this problem and I will be using it later down the line in my own 3D game projects. You can check out one of my games at: https://github.com/erichlof/SpacePong3D
Best of luck to you!
-Erich
Your ray start position is not good. Probably due to vertex coordinates being local to the plane. You start the raycast from inside the sphere so it never hits anything.
I changed the ray start position like this as a test and get 726 collisions:
var rayStart = new THREE.Vector3(0, 0, 500);
var ray = new THREE.Raycaster(rayStart, new THREE.Vector3(0, 0, -1));
Forked jsfiddle: http://jsfiddle.net/H5YSL/
I think you need to transform the vertex coordinates to world coordinates to get the position correctly. That should be easy to figure out from docs and examples.

Three.js - Rotation not respecting local orientation

I'm using a large array of objects built around a center point in a scene, and need to manipulate them all around their local axis. They are all facing the origin using a blank object and lookAt(), then I used this method to align the other axes correctly. Getting the initial rotation this way worked great, unfortunately when I try to rotate these objects on the fly with object.rotation.x = <amount>, it does not respect the local axis of the object.
The confusing part is, it's not even using the global axis, the axis it's using almost seems entirely arbitrary. I set up a JSFiddle to demonstrate this here. As you can see on line 129, looker.rotation.z works correctly, it rotates along the Z axis properly, but if it's changed to X or Y, it doesn't rotate along local or global axes. If anyone could demystify what is happening to cause this, that would be great.
What is happening is that you want to add some rotation to the current orientation, and setting the variable looker.rotation.z means other thing.
At the end, to calculate the rotation matrix of the looker, there will be something like (pseudocode: the functions are not these, but you get the idea):
this.matrix.multiply( makeXRotationMatrix(this.rotation.x) )
this.matrix.multiply( makeYRotationMatrix(this.rotation.y) )
this.matrix.multiply( makeZRotationMatrix(this.rotation.z) )
DrawGeometry(this.geom, this.matrix)
and composition of rotations are not intuitive. This is why it doesn't seem to follow any axis system.
If you want to apply a rotation in some axis to the existing matrix, it can be made with the functions rotateX (angle), rotateY (angle), rotateZ (angle), and rotateOnAxis (axis, angle). axis can be a THREE.Vector3.
Changing directly looker.rotation.z works because it is the nearest rotation to the geometry, and it will not be affected by the other rotations (remember that transformation matrices apply in inverse order, e.g. T*R*G is Rotating the Geometry, and then, Translating it).
Summary
In this case I suggest not to use the line:
looker.rotation.z += 0.05;
Use
looker.rotateZ (0.05);
or
looker.rotateX (0.05);
instead. Hope this helps :)

Three.js - Rotating a sphere around a certain axis

I have a problem. In Three.js, I want to rotate a sphere (Earth) around axis tilted by 23.5 degs. I found sphere.rotation.x, sphere.rotation.y and sphere.rotation.z, but when I combine them in the correct ratio, the sphere's rotation is quite weird - it has no permanent rotation axis. I think I need a function like sphere.rotation.vector(1,0,-1). Does anyone know how this function is called and how the correct syntax is?
Many thanks for answers!
You do not have to understand how Euler angles or quaternions work to do what you want. You can use
Object3D.rotateOnAxis( axis, angle );
Object3D.rotateOnWorldAxis( axis, angle );
Make sure axis is a unit vector (has length 1), and angle is in radians.
Object3D.rotateOnAxis( axis, angle ) rotates on an axis in object space.
Object3D.rotateOnWorldAxis( axis, angle ) rotates on an axis in world space.
three.js r.104
You need to use quaternions for this. This video explains what quaternions are and how they are used in 3D graphics.
You can construct a quaternion like this:
quaternion = new THREE.Quaternion().setFromAxisAngle( axisOfRotation, angleOfRotation );
Then you apply it to your object by:
object.rotation.set( new THREE.Euler().setFromQuaternion( quaternion ) );
You can also achieve this by using object hierarchies. For example, you can make an Object3D() instance and tilt it by 23.5 degs, then create a sphere (Earth) and add it to the tilted object. The sphere will then rotate around the tilted Y axis. Quaternions however, are the best tool for solving this.
var quaternion = new THREE.Quaternion();
var object = scene.getObjectByName('xxx');
function render(){
quaternion.setFromAxisAngle(new THREE.Vector3(0, 1, 0).normalize(), 0.005);
object.position.applyQuaternion(quaternion);
}
three.js version is 86, see full example on codepen.
You can rotate your sphere using th 'ObjectControls' module for ThreeJS that allows you to rotate a single OBJECT (or a Group), and not the SCENE.
Include the libary:
then
var controls = new THREE.ObjectControls(camera, renderer.domElement, yourMesh);
You can find here a live demo here: https://albertopiras.github.io/threeJS-object-controls/
Here is the repo: https://github.com/albertopiras/threeJS-object-controls.
Hope this helps

combine rotation and translation with three.js

i'm using Three.js (without shaders, only with existing objects methods) in order to realize animations, but my question is very simple : i'm sure it's possible, but can you tell me (or help me) how should i combine several animations on a shape ? For example, rotating and translating a sphere.
When i'm doing :
three.sphere.rotation.y += 0.1;
three.sphere.translateZ += 1;
the sphere rotates but the translation vector is also rotating, so the translation has no effect.
I know a bit openGL and i already have used glPushMatrix and glPopMatrix functions, so do them exist in this framework ?
Cheers
Each three.js object3D has a position, rotation and scale; the rotation (always relative to its origin or "center") defines its own local axis coordinates (say, what the object sees as its own "front,up, right" directions) and when you call translateZ, the object is moved according to those local directions (not along the world -or parent- Z axis). If you want the later, do three.sphere.position.z += 1 instead.
The order of transformation is important. You get a different result if you translate first and then rotate than if you rotate first and then translate. Of course with a sphere it will be hard to see the rotation.

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